PubMed Health⌕ Search

Biomedical subjects

J Lin

Publications and source records attributed to J Lin.

At least 343 records · Page 19Linked to original sources
PubMed1998

[The effects of different instrumentation on scoliosis].

OBJECTIVE: To investigate the effectiveness of the treatment of scoliosis with different surgical methods. METHOD: 125 cases of scoliosis less than 100 degrees treated during 14 years (1984 - 1997) were analyzed. Different operative methods were compared for their advantages and disadvantages, i.e. results and complications 10 months after operation and follow-up. RESULT: Harrington instrumentation was less effective in scoliotic curve correction and had more complications than other procedures. Luque technique needed longer operation time for wire passage at each level and had risk of neurological damage. CD and Zielke method showed 10% - 20% curve correction. No dislodgment of hook and fractured rods was found in the CD group. Anterior release plus posterior instrumentation was superior to other techniques. CONCLUSION: Treatment of scoliosis with anterior release plus posterior CD is practical for children before a new technique without spinal fusion is developed.

Adolescent↗
PubMed1998

[The role of L-arginine and L-citrulline in activated macrophage against Toxoplasma gondii infection in vitro].

AIM: To determine whether both the production of NO and the toxoplasmastatic or toxoplasmacidal activity of activated macrophages cultured in physiologic levels of arginine can be enhanced by increasing the availability of arginine, or citrulline. METHODS: After the activated M phi were infected with the RH strain of T. gondii, the levels of NO production, the infection rate of M phi and the number of tachyzoites in parasitophorous vacuoles were determined after the M phi were cultured in medium added with various concentrations of L-arginine or L-citrulline for 18 h. RESULTS: (1) The multiplication of intracellular toxoplasmic tachyzoites could be inhibited by activated macrophages, depending on the production of NO in the presence of physiologic levels of arginine. (2) Increased exogenous arginine or citrulline resulted in a significant elevation of NO production induced by activated macrophages and further reduction of infection rate of macrophages as well as inhibition of multiplication of intracellular tachyzoites. (3) Citrulline could fully substitute for arginine in enhancing NO production and toxoplasmastatic or toxopasmacidal activity. CONCLUSION: The physiological levels of arginine were able to induce sufficient intrinsic NO production to inhibit intracellular multiplication of toxoplasmatic tachyzoite but unable to protect cell from infection and that increasing the substrate levels for NO biosynthesis may enhance in vitro toxoplasmastatic or toxoplasmacidal activity of activated macrophages.

Animals↗
PubMed1998

[Appllcation of PYGC and the hierarchical clustering analysis to recognization of viruses].

The pyrolysis gas chromatography of 29 strains nuclear polyhedrosis viruses, 11 strains cytoplasmic polyhedrosis viruses and 16 strains granulosis viruses were performed on a shimadzu GV-9A capillary gas chromatography equipped with a pyrolyser model PYR-2A. The differences among the inclusion bodies of NPV, CPV and GV could clearly be distinguished and also beidentified through analysis of fingerprinting the hierarchical clustering analysis of GC, This procedure has provided a usefel method for the classification and identification of viruses.

Algorithms↗
PubMed1998

[Morphological observation of the endogenous endophthalmitis of cryptococcus neoformans].

PURPOSE: To observe the pathologic change of the endogenous endophthalmitis of cryptococcus neoformans. METHODS: Light and electron microscope were used. RESULT: The choroid was focally tumor-like by an inflammatory cells infiltrate, which consisted of multinucleated gicant, epithelioid cells and lymphocytes. Special stains (Grocott's methnamine silver, PAS, alcian blue) and electron microscope disclosed the budding form of cryptococcus neoformans. CONCLUSION: The morphologic examinations are only an effectivel method of diagrosing the endogenous endophthalmitis of cryptococcus neoformans.

Adult↗
PubMed1998

[The establishment, freezing-state preservation and resuscitation of retinoblastoma SO-Rb70 cell line].

PURPOSE: To establish a new cell line of human retinoblastoma (Rb), frozen and resuscitated to provide a Rb cell reservoir for clinical and experimental research. METHODS: The screening cells were washed and blown directly without centrifugation and then inoculated. Based on the cell-frozen principle, the Rb cell line was collected and established, then frozen in liquid nitrogen and resuscitated. RESULTS: SO-Rb70 cell line was established successfully. 8 groups of cells were frozen. The resuscitation experiment was carried out for 6 times, 4 times being successful. CONCLUSION: The preserved human Rb cells in liquid nitrogen grew normally after resuscitation with the maintenance of previous bioactivities and characteristics. This research helped to provide abundant material for further study of Rb.

Cell Line↗
PubMed1998

Pulsatile insulin release: role of cytoplasmic Ca2+ oscillations.

Oscillations of plasma insulin are essential for the hypoglycaemic effect of the hormone. Disturbance and partial loss of these oscillations occur during the development of Type 2 diabetes, in association with down-regulation of insulin receptors and insulin resistance. Oscillations with a frequency similar to that of plasma insulin have been observed in the cytoplasmic Ca2+ concentration ([Ca2+]i) of pancreatic beta cells, indicating that the ion plays a role in generating insulin pulses. Studies of individual islets have revealed that oscillations of [Ca2+]i and insulin release are synchronous. However, insulin release is also pulsatile under conditions in which [Ca2+]i is stable. These results support the notion that variations in the ATP/ADP ratio are sufficient to induce pulsatile insulin release. Under physiological conditions, this pulsatility may depend on the synergistic effects of ATP/ADP and [Ca2+]i oscillations.

Animals↗
PubMed1998

Biomechanical comparison of antegrade and retrograde nailing of humeral shaft fracture.

A pair-controlled study was conducted to compare biomechanical properties of antegrade and retrograde nailing of humeral fractures. First, six paired fresh anatomic specimen humeri were used to compare the properties of humeri fractured at the middle to distal diaphyses junction that were nailed from the retrograde approach with the Humeral Locked nail with those of contralateral intact humeri. An 18 additional pairs were divided into three equal groups by distal, proximal, or mid-diaphysis location of a standardized 5-mm bone defect to simulate unstable fractures. The retrograde and antegrade nailings were performed in each pair in a random manner. Nail and bone constructs were tested for bending stiffness by nondestructive three-point bending and for torsional stiffness by destructive torsional tests. Compared with intact humeri, fractured humeri fixed with nails had 28.6% posteroanterior and 31.4% mediolateral bending stiffness, 22.5% torsional stiffness, and 43.3% failure torque. For distal fractures, retrograde nailing showed significantly more initial stability and higher bending and torsional stiffness; for proximal fractures, antegrade nailing showed similar properties. For middle to distal diaphyses junction fractures, retrograde and antegrade nailing were indistinguishable. The defect created as an entry portal for retrograde nailing reduced the bone strength only 11.1%. These results suggest that retrograde nailing, which is less detrimental to shoulder function than is antegrade nailing, is an acceptable alternative treatment for humeral shaft fractures. In addition, nailing from the short to the long bone segments can improve mechanical properties of the fixation construct because of better nail and bone interface purchase.

Biomechanical Phenomena↗
PubMed1998

Neurochemical and behavioral effects of ciproxifan, a potent histamine H3-receptor antagonist.

Ciproxifan, i.e., cyclopropyl-(4-(3-1H-imidazol-4-yl)propyloxy) phenyl) ketone, belongs to a novel chemical series of histamine H3-receptor antagonists. In vitro, it behaved as a competitive antagonist at the H3 autoreceptor controlling [3H]histamine release from synaptosomes and displayed similar Ki values (0.5-1.9 nM) at the H3 receptor controlling the electrically-induced contraction of guinea pig ileum or at the brain H3 receptor labeled with [125I]iodoproxyfan. Ciproxifan displayed at least 3-orders of magnitude lower potency at various aminergic receptors studied in functional or binding tests. In vivo, measurement of drug plasma levels, using a novel radioreceptor assay in mice receiving ciproxifan p.o. or i.v., led to an oral bioavailability ratio of 62%. Oral administration of ciproxifan to mice enhanced by approximately 100% histamine turnover rate and steady state level of tele-methylhistamine with an ED50 of 0.14 mg/kg. Ciproxifan reversed the H3-receptor agonist induced enhancement of water consumption in rats with and ID50 of 0.09 +/- 0.04 mg/kg, i.p. In cats, ciproxifan (0.15-2 mg/kg, p.o.) induced marked signs of neocortical electroencephalogram activation manifested by enhanced fast-rhythms density and an almost total waking state. In rats, ciproxifan enhanced attention as evaluated in the five-choice task performed using a short stimulus duration. Ciproxifan appears to be an orally bioavailable, extremely potent and selective H3-receptor antagonist whose vigilance- and attention-promoting effects are promising for therapeutic applications in aging disorders.

Animals↗
PubMed1998

Primary ureteral carcinoma. Report of 15 cases and comparison of the effectiveness of diagnostic methods.

Fifteen cases of primary urothelial carcinomas of the ureter are reported (14 transitional cell carcinoma and 1 mixed transitional cell carcinoma and squamous cell carcinoma). There was a clear male predominance (11/4); the peak incidence was in the sixth decade. Most tumors originated from the distal third of the ureter. Multicentricity and high recurrence rate after partial ureterectomy were noted. The clinical signs were hematuria and flank pain. Urine cytology and IVU were diagnostic in a limited number of cases. Retrograde pyelography was very helpful. CT showed to be the image modality of choice for diagnosis and preoperative staging.

Aged↗
PubMed1997

Kinase-independent potentiation of B cell antigen receptor-mediated signal transduction by the protein tyrosine kinase Src.

Signal transduction mediated by the B cell Ag receptor involves the activation of multiple protein tyrosine kinases that are members of the Src family (i.e., Fyn, Lyn, Blk, Lck). To determine whether members of the Src family possess common physical and/or enzymatic properties that enable them to potentiate signal transduction via the B cell Ag receptor, we expressed the protein tyrosine kinase Src in the B lymphoma cell line K46-17 mu m lambda. Based on coprecipitation analysis and two-color immunofluorescence, this heterologous Src family kinase was observed to physically associate with the B cell Ag receptor. Additional experiments demonstrated that B cell Ag receptor cross-linking results in increased tyrosine phosphorylation and activation of Src. Several parameters of B cell activation, including tyrosine phosphorylation of intracellular substrates, calcium mobilization, and transcription factor activation, were potentiated in cells that expressed Src when compared with control cells. To determine whether potentiation of Ag receptor-mediated signaling by Src was dependent on its catalytic activity, a kinase-deficient form of Src was expressed in K46-17 mu m lambda cells. Transfectants expressing kinase-deficient Src exhibited an enhanced responsiveness to stimulation through the B cell Ag receptor that was comparable with transfectants expressing wild-type Src. Additionally, kinase-deficient Src was observed to associate with the endogenous kinase Lyn in an activation-dependent manner. These findings indicate that members of the Src family may potentiate Ag receptor-mediated signaling via a kinase-independent mechanism(s) that involves amplification of kinase recruitment to the Ag receptor activation complex.

Adjuvants, Immunologic↗
PubMed1997

Genomic structures of cardiotoxin 4 and cobrotoxin from Naja naja atra (Taiwan cobra).

Two genomic DNAs with the size of 2.3 kb and 2.4 kb, which were isolated from the liver of Naja naja atra (Taiwan cobra), encoded the precursors of cardiotoxin 4 and cobrotoxin, respectively. Both genes shared virtually identical overall organization with three exons separated by two introns, which were inserted in the similar positions of the gene's coding regions. Moreover, their nucleotide sequences shared approximately 84.2% identity. This result reveals the evolutionary relationship between cardiotoxin and cobrotoxin. The exon/intron structures of cardiotoxin 4 and cobrotoxin genes were similar to that reported for erabutoxin c gene, a neurotoxin genomic DNA from a sea snake (Laticauda semifasciata). However, in contrast to the finding that the intron 2 of these genes had a similar size, a notable variation with the size of intron 1 was observed (1233 bp, 1269 bp and 197 bp for cardiotoxin 4, cobrotoxin and erabutoxin c genes, respectively). The different size with intron 1 is due to the middle region at the first intron of cardiotoxin 4 and cobrotoxin genes, which encoded small nucleolar RNA (snoRNA), being absent in that of erabutoxin c gene. These results, together with the finding of the potential mobility of snoRNA genes during evolution, suggest that intron insertions or deletions of snoRNA genes occur with the evolutionary divergence of snake neurotoxins and cardiotoxins.

Amino Acid Sequence↗
PubMed1997

Both lumenal and cytosolic gating of the aqueous ER translocon pore are regulated from inside the ribosome during membrane protein integration.

Portions of the nascent chain are exposed to the lumen, the cytosol, or neither at different stages during the cotranslational integration of a protein into the ER membrane, as shown by compartment-specific collisional quenching of fluorophores incorporated into the polypeptide. The opening or closing of each end of the aqueous translocon pore is tightly controlled and occurs in a sequence that does not compromise the membrane's permeability barrier. Surprisingly, these structural changes at the membrane are effected by the transmembrane segment in the nascent protein from inside the ribosome. Thus, the ribosome, not the translocon, first recognizes the transmembrane segment and triggers long-range structural changes at the translocon that may be involved in shifting its function from translocation to integration.

Animals↗
PubMed1997

A new concept for the mechanism of action of chymotrypsin: the role of the low-barrier hydrogen bond.

The basicities of the diad H57-D102 at N(epsilon)2 in the tetrahedral complexes of chymotrypsin with the peptidyl trifluoromethyl ketones (TFK) N-acetyl-L-Leu-DL-Phe-CF3 and N-acetyl-DL-Phe-CF3 have been studied by 1H-NMR. The protons bridging His 57 and Asp 102 in these complexes are engaged in low-barrier hydrogen bonds (LBHBs). In 1H-NMR spectra at pH 7.0, these protons appear at delta 18.9 and 18.6 ppm, and the pK(a)s of the diads are 12.0 +/- 0.2 and 10.8 +/- 0.1, respectively. The difference indicates that removal of leucine from the second aminoacyl site S2 of chymotrypsin weakens the LBHB and decreases the basicity of the H57-D102 diad relative to the case in which S2 is occupied by leucine. Consideration of the available structural data on chymotrypsin and other serine proteases, together with the high pK(a)s of the hemiketals formed with TFKs, suggests that LBHB formation in catalysis arises through a substrate-induced conformational transition leading to steric compression between His 57 and Asp 102. Because the N-O distance in the LBHB is shorter than the Van der Waals contact distance, the LBHB is proposed to stabilize the tetrahedral intermediate through relief of steric strain between these residues. In this mechanism, substrate-induced steric compression within the diad increases the basicity of N(epsilon)2 in His 57, making it a more effective base for abstracting a proton from Ser 195 in the formation of the tetrahedral intermediate. The values of pK(a) for N(epsilon)2 in TFK adducts lie between those of Ser 195 (pK(a) approximately 14) and the leaving group in tetrahedral adducts (pK(a) approximately 9), making N(epsilon)2 of the H57-D102 diad strong enough as a base to abstract the proton from Ser 195 in tetrahedral adduct formation but not so strong that its conjugate acid cannot protonate the leaving group. According to this theory, the "normal" pK(a) of His 57 in free chymotrypsin arises from the use of part of the stabilization energy provided by the LBHB to drive the conformational compression required for its formation. In catalysis, the energy for conformational compression is supplied by the binding of remote portions of the substrate, including the side chains of P1 and P2.

Animals↗
PubMed1997

Solution structure of the quaternary MutT-M2+-AMPCPP-M2+ complex and mechanism of its pyrophosphohydrolase action.

The MutT enzyme (129 residues) catalyzes the hydrolysis of nucleoside triphosphates (NTP) by substitution at the rarely attacked beta-P, to yield NMP and pyrophosphate. It requires two divalent cations, forming an active E-M2+-NTP-M2+ complex. The solution structure of the free enzyme consists of a five-stranded mixed beta-sheet connected by loop I-alpha-helix I-loop II, by two tight turns, and by loop III and terminated by loop IV-alpha-helix II [Abeygunawardana, C., et al. (1995) Biochemistry 34, 14997-15005]. Assignments of backbone 15N and NH resonances and side chain 15N and NH2 resonances of the quaternary complex were made by 1H-15N HSQC titrations of the free enzyme with MgCl2 followed by equimolar AMPCPP/MgCl2. H(alpha) assignments were made by 1H-15N 3D TOCSY HSQC, and 1H-13C CT-HSQC spectra and backbone and side chain 1H and 13C assignments were made by 3D HCCH TOCSY experiments. Ligands donated by the protein to the enzyme-bound divalent cation, identified by paramagnetic effects of Co2+ and Mn2+ on CO(C)H spectra, are the carboxylate groups of Glu-56, -57, and -98 and the amide carbonyl of Gly-38. The solution structure of the complex was computed with XPLOR using a total of 2168 NOE and 83 phi restraints for the protein, 11 intramolecular NOEs for bound Mg2+ AMPCPP, 22 intermolecular NOEs between MutT and AMPCPP, and distances from the enzyme-bound Co2+ to the three phosphorus atoms of Co3+(NH3)4AMPCPP from paramagnetic effects of Co2+ on their T1 values. The fold of the MutT enzyme in the complex is very similar to that of the free enzyme, with minor changes in the metal and substrate binding sites. The adenine ring binds in a hydrophobic cleft, interacting with Leu-4 and Ile-6 on beta-strand A and with Ile-80 on beta-strand D. The 6-NH2 group of adenine approaches the side chain NH2 of Asn-119. This unfavorable interaction is consistent with the stronger binding by MutT of guanine nucleotides, which have a 6-keto group. The ribose binds with its hydroxyl groups oriented toward the solvent and its hydrophobic face interacting with Leu-4, Ile-6, and the gamma-CH2 of Lys-39 of loop I. The metal-triphosphate moiety appears to bind in the second coordination sphere of the enzyme-bound divalent cation. One of two intervening water ligands is well positioned to attack P(beta) with inversion and to donate a hydrogen bond to the conserved residue, Glu-53, which may deprotonate or orient the attacking water ligand. Lys-39 which is positioned to interact electrostatically with the alpha-phosphoryl group may facilitate the departure of the leaving NMP. On the basis of the structure of the quaternary complex, a mechanism of the MutT reaction is proposed which is qualitatively and quantitatively consistent with kinetic and mutagenesis studies. It is suggested that similar mechanisms may be operative for other enzymes that catalyze substitution at P(beta) of NTP substrates.

Adenosine Triphosphate↗